The invention relates to a fastening device for heat-protection shields. More particularly, the invention relates to a fastening device for fastening heat-protection shields in a turbo machine.
Heat-protection shields are used in thermal turbomachines, such as gas turbines for example. They are arranged there in the axial direction between the blade rows and protect the rotor or the casing from direct contact by hot gas.
During operation, these components must absorb considerable thermal differential expansions with the component to which they are fastened, as a result of which they are deformed in the radial and axial directions. On the other hand, heat-protection shields, in the installed state, have only very small clearance relative to the blades opposite them. On account of the deformation and the small clearance, however, there is the risk of the blades grazing against the heat-protection shield. This results in a further heat input and in a positive reaction via a greater deformation and even more violent grazing. Under unfavorable conditions, this may lead to serious damage to a machine. However, the heat-protection shield must be allowed a certain clearance in its mountings, since impaired thermal expansions otherwise lead to high component internal stresses and finally to a drastic reduction in the service life of the heat-protection shield. Accordingly, according to the prior art, the well-known latent risk of damage due to the grazing of a component moving in a relative manner against a heat-protection shield has to be tolerated.
The intention of the invention is to provide a remedy here. The object of the invention, as characterized in the claims, is to permit deformations in a heat-protection shield to a certain extent in order to compensate for thermal expansions but to definitely limit in particular radial deformations to a well-defined size.
The essence of the invention is therefore to fix a heat-protection shield in the casing or to the shaft of a turbomachine by means of mounting elements situated axially on the outside and, by means of additional mounting elements arranged between the latter, to provide a safety device for absorbing excessive radial deformations. In every axial section of the heat-protection shield, in each case only one mounting element performs an axial fixing function, whereas the other mounting elements permit an unimpaired axial deformation of the heat-protection shield. Furthermore, the heat-protection shield in axial section is fixed in the radial direction by the mounting elements situated furthest on the outside. The radial mounting of the heat-protection shield at two points far away from one another improves the tilting stability of the mounting on the one hand. On the other hand, the axial overhang of the heat-protection shield is minimized, as a result of which vibrations of the heat-protection shield are best prevented. Arranged in the axial direction between the radially bearing mounting elements are further mounting elements which have a radial clearance in their fastening slots and have no bearing function during normal operation. This mounting element is given a bearing function and prevents the occurrence of an excessive radial deformation only when a radial deformation of the heat-protection shield exceeds the size of the radial clearance where one of these mounting elements is arranged with this clearance.